Large trailers, such as those used in the freight industries, are equipped with braking systems in order to ensure that the tractor and trailer combination has enough braking power to safely transit on roads. Some trailers are commonly equipped with air brakes that are actuated from the tractor, which air brakes automatically lock the wheels of the trailer when the latter is unhitched.
Smaller trailers, for instance domestic trailers or trailers used to tow recreational vehicles (e.g., boat, motorcycle, ATV, etc.) may have brake systems. For instance, electric drum brakes are commonly used in smaller trailers. In a drum brake, shoes (a.k.a., pads) press against a rotating drum-shaped part called a brake drum. The brake drum rotates, as part of the wheel. In order to apply the braking power to the drum brake, an electromagnetic magnet is powered to activate a displacement of the shoes into contact with the drum.
Accordingly, an electric current must be supplied to the electric drum brake to apply the brakes. When the trailer is unhitched, the electric drum brake may often be disconnected from the power source of the vehicle. Accordingly, random masses (e.g., log, plank, rock) are often wedged behind the wheels of the trailer so as to block movement of the trailer. This action of wedging is hazardous. Moreover, if the operator forgets to wedge a mass behind the wheels, the trailer might start moving if it is on a slope. With the inertia of the trailer and its contents, a moving trailer is hard to stop and may cause severe damages and/or injuries.
Hence, a safety brake system has been developed to address this issue, and is described in PCT application publication no. WO 2010/096934. The safety brake system detects an unhitched condition of the trailer and produces a mechanical force to apply the brakes in response thereto. However, in electric drum brakes, an electric current must be supplied to apply the brakes, which electric current may not be available due to the unhitching of the trailer from the vehicle. Moreover, electric drum brakes may not be configured to receive electric current for an extended period (e.g., parked trailer). This would require a continuous supply of power and batteries of suitable capacity.